1. Field of the Invention
The present invention relates to a novel urea-urethane compound. The present invention relates also to a novel color-producing composition obtained by using the urea-urethane compound, and a recording material obtained by using the color-producing composition.
The color-producing composition of the present invention is useful as a color-producing composition for recording materials used by means of recording energy such as heat, pressure or the like, and the present invention relates to, in particular, a color-producing composition capable of giving an improved storage stability to an uncolored portion (an original recording material surface) and a developed color image, and a recording material, in particular, a heat-sensitive recording material, which is obtained by using the color-producing composition.
2. Description of the Related Art
Various chemical color-producing systems used by means of recording energy such as heat, pressure or the like have been known. Of these systems, color-producing systems usually composed of a two-component color-producing system consisting of a colorless or light-colored dye precursor and a developer capable of causing color development on contact with the dye precursor have been known since early times and are commonly utilized in recording materials. There are, for example, pressure-sensitive recording materials used by means of pressure energy, heat-sensitive recording materials used by means of heat energy, and light-sensitive recording materials used by means of light energy.
Pressure-sensitive recording materials used by means of pressure energy have been very generally used as if they were plane paper. In general, the pressure-sensitive recording material is obtained by dissolving a dye precursor in a suitable solvent, emulsifying the resulting solution to several microns, and making the emulsion into microcapsules. Upper paper obtained by coating a substrate with the microcapsules and under paper obtained by coating another substrate with a developer layer containing a developer are placed one upon the other so that the microcapsule-coated surface and the developer-coated surface may face each other. When a pressure is applied to the resulting assembly by writing, striking or the like, the microcapsules are destroyed to release the contents including the dye precursor. The dye precursor transfers to the developer layer to come into contact with the developer, so that color development reaction occurs, resulting in recording of an image.
In recent years, a heat-sensitive recording method comprising recording by means of heat energy has been often adopted in various information machines such as facsimiles, printers, recorders and the like. A heat-sensitive recording material used in the heat-sensitive recording method has many excellent characteristics such as a high whiteness, appearance and feel which are similar to those of plane paper, and excellent aptitudes for recording, for example, a high color development sensitivity. The heat-sensitive recording method is advantageous, for example, in that an apparatus used in the method is small, requires no maintenance and produces no noise. Therefore, the range of use of the heat-sensitive recording method have been increased in various fields of, for instance, recorders for measurement, facsimiles, printers, terminals of computer, labels, and automatic vending machines for railroad tickets or the like.
In the heat-sensitive recording method, a recording material obtained by forming on a substrate a color-producing layer containing a two-component color-producing composition is mainly used, and the components of the heat-sensitive composition are brought into contact with each other by treating the recording material with heat supplied as recording energy from a thermal head, a hot stamp, laser beams or the like. Many of compositions used as the color-producing composition are those obtained by using a colorless or light-colored, electron-donating dye precursor (in particular, a leuco dye) and an acidic developer such as a phenolic compound. An example of recording material obtained by using a leuco dye is thermal paper obtained by using a combination of Crystal Violet lactone and 4,4′-isopropylidenediphenol (bisphenol A) as a heat-sensitive color-producing composition (see U.S. Pat. No. 3,539,375, etc.).
As the dye precursor and developer used in each of the recording methods described above, an electron-donating compound and an electron-accepting compound, respectively, are mainly used. This is because the electron-donating compound and the electron-accepting compound have, for example, the following excellent characteristics: the dye precursor as electron-donating compound and the developer as electron-accepting compound come into contact with each other to give a developed color image with a high density in a moment; and a nearly white appearance can be obtained and various hues such as red, orange, yellow, green, blue, black, etc. can be obtained. However, the developed color image obtained is so poor in chemical resistance that the record disappears easily on contact with a plasticizer contained in a plastic sheet or an eraser, or a chemical contained in food or cosmetics, and the developed color image is so poor in record storage stability that the record fades or, what is worse, disappears when exposed to sunlight for a relatively short period of time. Therefore, color-producing compositions comprising the dye precursor and the developer are limited in their use to a considerable extent, and their improvement is eagerly desired.
In recent years, phenolic compounds represented by bisphenol A are considered unsuitable for use because they are likely to be endocrine disrupters, and hence a non-phenolic developer is requested.
For fulfilling such a request, for example, JP-A-59-115,887 and U.S. Pat. No. 4,521,793 disclose recording materials comprising a combination of color-producing compositions comprising an aromatic isocyanate and an imino compound, as recording materials having a high shelf stability. These references disclose various recording materials in which the two color-producing compositions are brought into contact with each other to be reacted, by application of recording energy such as heat, pressured, light or the like. The references describe the fact that various colors such as red, orange, yellow, light brown, dark brown, etc. can be developed by properly selecting the color-producing compositions. However, in the inventions disclosed in the references, the development of a black color is not yet sufficient which is eagerly desired in the case of recording materials commonly used at present.
JP-A-8-2,111 and JP-A-8-2,112 disclose heat-sensitive recording materials having a color-producing layer containing a colorless or light-colored dye precursor and a urea compound, as heat-sensitive recording materials obtained by using a non-phenolic developer. These recording materials, however, give a low coloring density and have an insufficient shelf stability.
JP-A-5-116,459 discloses a heat-sensitive recording material having a heat-sensitive color-producing layer containing a colorless or light-colored dye precursor and a sulfonylurea compound. This recording material, however, gives a low whiteness and has an insufficient shelf stability.